Spring MVC更改<form:select>选项与其他动态<form:select>

Question

我正在使用Spring MVC平台，并且遇到了问题。 我希望允许用户发送他们在平台上添加的约定和事件的邀请。我为这两个人都有model，他们工作的很好，但是当向别人发送邀请时，我似乎无法找到动态更新<form:select>选项列表的方式。 当一个人邀请他人参加一个约定时，他们有两个下拉列表。第一个是约定下拉列表，它包含该人员添加的所有约定。每个Convention都有一个Event s的列表，第二个下拉列表应显示所选约定的所有事件。 因此，对于第一个下拉列表中的每个选项，第二个下拉列表中应该有多个选项。

我会在这里发布模型，如果它们对你来说意味着什么，并且削减与这个问题无关的代码。

事件：

public class Event { 

     @Id 
     @GeneratedValue 
     private int eventId; 
     private int conventionId; 
     private String conventionName; 

     private String eventName; 
     private String eventDescription; 
     private String websiteLink, facebookLink, twitterLink, instagramLink, youtubeLink; 
     private String eventType; 
     private String eventDateFrom; 
     private String eventDateTo; 
     private String hostedBy; 
     private String eventAddress; 
     private String eventPr; 
    //getters and setters 

公约：

@Entity 
public class Convention { 

    @Id 
    @GeneratedValue 
    private int conventionId; 

    private String conventionName; 
    private String conventionDescription; 


    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL) 
    private List<Event> conventionEvents; 
    private String websiteLink, facebookLink, twitterLink, instagramLink, youtubeLink; 
    private String conventionType; 
    private String conPr; 
    private String hostedBy; 
    private boolean isAccepted; 
//getters and setters 

邀请：

@Entity 
public class Invite { 
    @Id 
    @GeneratedValue 
    private int inviteId; 

    private String senderName; 
    private int senderId; 
    @NotEmpty(message = "Convention name must not be empty!") 
    private String conName; 
    private String eventName; 
    @NotEmpty(message = "Message must not be empty!") 
    private String message; 
    private String tripType; 
    private String dateFrom; 
    private String dateTo; 
    private boolean isRead; 
    private String sendingTo; 

sendInvite.jsp [编辑 - 改变了代码]

 <%@ include file="/WEB-INF/views/template/header.jsp" %> 
    <form:form action="${pageContext.request.contextPath}/sendInvite/{${sendingTo}}" method="post" commandName="invite"> 
     <form:hidden path="senderName" value="${pageContext.request.userPrincipal.name}"/> 
     <form:hidden path="sendingTo" value="${sendingTo}"/> 

     <div class="form-group"> 
      <label for="eventName">Convention: </label> 
     </div> 


     <form:select path="conName" name="conName"> 

      <c:forEach items="${conventionList}" var="convention"> 
       <form:option value="${convention.conventionName}">${convention.conventionName}</form:option> 
      </c:forEach> 
     </form:select> 

     <form:select path="eventName"> 
      <c:forEach items="${eventList}" var="event"> 
       <c:if test="${event.conventionName == convention.conventionName}"> 
        <form:option value="${event.eventName}">${event.eventName}</form:option> 
       </c:if> 
      </c:forEach> 
     </form:select> 

//HERE I JUST NEED TO FIND A WAY TO GET " <c:if test="${event.conventionName == convention.conventionName}">" WORKING SINCE I CAN'T GET THE ACTUAL VALUE OF THE CONVENTION NAME.// 


     <div class="form-group"> 
      <label for="message">Message body</label> 
      <form:textarea path="message" id="message" class="form-Control"/> 
     </div> 

     <div class="form-group"> 
      <label for="tripType">Trip type</label> 

      <form:select path="tripType" name="tripType"> 
       <form:option value="Paid">Paid</form:option> 
       <form:option value="Unpaid">Unpaid</form:option> 
       <form:option value="To be agreed">To be agreed</form:option> 

      </form:select> 
     </div> 
     <br><br> 

     <input type="submit" value="Send invitation" class="btn btn-default"> 
    </form:form> 
    </body> 
    </html> 

预先感谢您。

[编辑 - 添加InviteController]

@Controller 
public class InviteController { 

    @Autowired 
    InviteService inviteService; 

    @Autowired 
    ProfileService profileService; 

    @Autowired 
    ConventionService conventionService; 

    @Autowired 
    EventService eventService; 

    @RequestMapping("/sendInvite/{sendingTo}") 
    public String sendInvite(@PathVariable("sendingTo") String sendingTo, Model model, Principal principal) { 
     Invite invite = new Invite(); 
     List<Convention> conventionList = conventionService.getConventionsByUsername(principal.getName()); 
     List<Event> eventList = eventService.getEventListForOwner(principal.getName()); 
     model.addAttribute("eventList", eventList); 
     model.addAttribute("conventionList", conventionList); 
     model.addAttribute("invite", invite); 

     return "sendInvite"; 
    } 

    @RequestMapping(value = "/sendInvite/{sendingTo}", method = RequestMethod.POST) 
    public String sendInvitePost(@ModelAttribute("invite") Invite invite, @PathVariable("sendingTo") String sendingTo, Model model) { 
     model.addAttribute("sendingTo", sendingTo); 
     inviteService.addInvite(invite); 
     return "sendInviteSuccess"; 
    } 

} 

服务的方法名是自我解释，我只是得到一个列表用某种标准，无论是用户名或约定。

Answer 1

在你的实体，你已经宣布事件的列表，那么你就可以访问你这样的活动convetionList.eventName

<div class="form-group"> 
    <label for="eventName">Event: </label> 
    <form:select path="conName" name="conName" items="${conventionList.eventName}"/> 
</div> 

[编辑]

尝试修改从控制器的响应：

@RequestMapping("/sendInvite/{sendingTo}") 
public String sendInvite(@PathVariable("sendingTo") String sendingTo, Model model, Principal principal) { 


    List<Convention> conventionList = conventionService.getConventionsByUsername(principal.getName()); 
    List<Event> eventList = eventService.getEventListForOwner(principal.getName()); 

    for(Covention convention : conventionList){ 

     for(Event event : eventList){ 

      if(convention.getConventionId() == event.getConventionId()) 
      { 
       convention.conventionEvents.add(event);   

      } 
     } 


    } 
    //Now you have all of your events associated to your conventions 
    model.addAttribute("conventionList", conventionList); 
    model.addAttribute("invite", new Invite()); 

    return "sendInvite"; 
} 

现在，你应该能够使用${conventionList.conventionName}让所有约定在下拉列表视图和${conventionList.conventionsEvents.eventName}这个对象应按照惯例以dinamically方式显示

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